Program (or method) to compare two large folders

[SevenOfNine]

I need to compare 2 very large folders. One is a backup of the other, so I expect them to be identical, but I want to verify that each file is truly identical (byte for byte).

The folders have many subfolders and thousands of files, some over 1GB is size. So the solution must operate as fast as possible so it doesn't take days.

All I need to know is if there are any differences, and if so, which files are different. I don't need to know what is different within any files. If a file is different, I'll deal with that manually.

How can I do this? I'm fine using tools built into Windows 7 SP1, or using a piece of free software.

 

[Callender]

Well you could use copy changed files to get a report of files that exist in one directory but not the other.

Here's a comparison of my 64bit Programs directory compared with a mounted system image backup copy.

Test copy with no files actually moved.

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So that's 8000+ files in each 2.5Gb directory compared in about 30 seconds.

If you use binary compare it will be a little slower.

Another utility I use is WinMerge but it's not really fast when comparing huge directories.